The support comes as the Obama administration is working to build support to ensure it will get the 67 votes necessary to ratify the treaty. Obama has made clear the treaty is one of his top priorities during the lame-duck Congress.

But Republicans have voiced some reservations about the treaty, and their support would be critical in ensuring ratification. Sen. Jon Kyl's (R-Ariz.) led the opposition to the treaty.

The White House has expressed optimism that they'll lock up the necessary votes before the end of the lame-duck Congress, though the timing could be difficult coming up against the Senate's busy, end-of-year schedule.